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Proposed that matter is made of indivisible “atoms” (atomos), a philosophical model, not experimental. This was very early “atomism.”
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A long conflict between Athens and Sparta that reshaped ancient Greece. Athens lost power, and Sparta briefly became dominant. The war weakened all Greek city-states, setting the stage for later Macedonian conquest.
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Dalton’s atomic theory: atoms of each element are identical in mass, different elements have different atoms, compounds form by fixed whole-number ratios, and atoms are rearranged in reactions (not destroyed).
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A series of major European wars led by Napoleon Bonaparte. France fought coalitions of European powers, dramatically changing borders, governments, and military tactics throughout Europe. These wars shaped the political landscape for decades.
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While not directly about the atomic model, Faraday’s work laid the foundation for understanding electric charge, fields, and electrons. His insights were crucial for later atomic and subatomic theory.
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His discovery showed there were positively charged particles in atoms (ions), not just electrons. This added to the complexity of atomic structure and helped later in the identification of protons.
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Proposed the “plum pudding” model: the atom is a diffuse positive charge with electrons embedded throughout. This was the first model with subatomic particles.
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A conflict between the United States and Spain. The U.S. gained control of Puerto Rico, Guam, and the Philippines. The war marked the emergence of the U.S. as a major world power and shifted global naval influence.
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He showed that most of the atom’s mass is concentrated in a tiny, positively charged nucleus and that most of the atom is space.
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His “solar system” model introduced the idea that electrons occupy discrete energy levels. Electrons can jump between orbits, emitting or absorbing photons, which explains atomic spectra.
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Measured the electric charge of a single electron precisely. Showed that all measured charges were multiples of a “fundamental charge,” the electron’s charge.
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Tensions in Europe were rising due to alliances, militarism, nationalism, and imperial competition. The assassination of Archduke Franz Ferdinand in 1914 triggered WWI shortly after Rutherford proposed the nuclear model.
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His model replaced fixed orbits with probability distributions. Electrons are described by wavefunctions, which tell us the chance of finding an electron in a region (“electron cloud”).
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He showed that you cannot know both the exact position and momentum of an electron simultaneously. This further supports the “cloud” model: electrons don’t follow precise paths, but clouds of probability.
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A worldwide economic crisis marked by massive unemployment, bank failures, and severe poverty. Scientific funding was strained, and political instability increased across many nations.
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Discovered the neutron, proving that atoms contain a neutral particle in the nucleus. This explained why atomic mass didn’t match proton count and completed the modern nuclear model.
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A global conflict involving most major nations. Atomic science played a major role, as Chadwick’s neutron discovery made nuclear fission possible. His work directly led to the development of nuclear reactors and the atomic bomb.